Threats to Native Habitats

Mile-a-minute weed grows rapidly, reputedly up to six inches per day, sprawling over other vegetation and blocking sunlight. Thickets of mile-a-minute weed can reduce plant diversity in natural areas and degrade wildlife habitat. It is particularly aggressive in riparian areas (land adjacent to rivers and streams), a habitat type that many animal species depend upon. Mile-a-minute weed is a threat to tree regeneration in open areas such as plantations and nurseries. The species spreads via birds and waterways. Birds eat the abundant fleshy berries and spread the seeds in their droppings. Birds are probably responsible for the spread of this species along power lines and fencerows and in old fields. The berries float, which probably helps spread the plant along stream corridors. These efficient methods of spread have helped this invader become widely distributed in a relatively short period of time.

Description

Mile-a-minute weed is an herbaceous, annual trailing vine. Like most other members of the buckwheat family, it has alternate, undivided leaves, and relatively tiny, inconspicuous white flowers. Stems are armed with rows of small, rigid downward pointing barbs that are also present on the veins on the underside of the leaf blades. The barbs are substantial enough to lacerate bare hands when attempting to pull up the plants. The leaves are triangular, one to three inches in length, and typically pale green. There is a structure, called an ocrea, at the base of each petiole or leaf stem that completely encircles the main stem. On mile-a-minute weed, the structure is broad and leaf-like, which distinguishes this species from our native buckwheats. The fruits are bright blue, fleshy, and about the size of a pea.

Habitat

Mile-a-minute weed is most aggressive in areas with lots of sunlight and moist soils. Where it is established, it is often found in edges of woods, stream corridors, riverine islands, fencerows, roadsides, uncultivated fields, and other similar areas. Shade appears to be a limiting factor for this species. Climbing over other plants is a strategy that helps mile-a-minute weed reach sunnier areas while outcompeting other plants.

Distribution

The native range of this species in Asia. In the U.S. it has naturalized in a number of states in the northeast extending from New York south to Virginia, and west to Ohio. It has also appeared in several other states in other regions of the country. Mile-a-minute weed was first reported in North America from Portland, Oregon in 1890, where it apparently did not survive. It was not until the late 1930s that it naturalized and became invasive at a nursery in York County, Pennsylvania. It apparently arrived at the nursery as a hitchhiker with other imported plants; the owner of the nursery was curious about the plant and let it grow. It wasn’t long before the plant was out of control and the opportunity for eradication was lost. Based on the plant’s ecology, it is estimated that it could be a problem for most areas of the United States.

Control

Mechanical: Hand-pulling is an option for newly infested or lightly infested areas. As mile-a-minute weed is an annual, it is recommended that hand-pulling be conducted before seeds set, which occurs by August. Hand-pulling may be easiest when the plants are relatively young and have not had time to develop into extensive intertwined thickets. Note that the rows of small barbs on the plants will easily cut exposed flesh. Wear thick gloves and clothes for work with this invader. Sites cleared of mile-a-minute weed should be periodically resurveyed, as new plants may start as late as July. A return visit the following year is also recommended to ensure that no stray plants were overlooked. Mowing or cutting repeatedly during the growing season is an alternative to hand-pulling. This will keep the plants from developing flowers and seeds, and thus prevent the following year’s growth.

Chemical: For larger infestations, an application of a glysophate-based herbicide is a more practical method for eradicating the plants. Glysophate is a nonspecific herbicide and will damage any vegetation it comes in contact with so avoid overspraying. Use herbicides responsibly and follow the manufacturer’s directions. Contact the Maine Department of Agriculture for information on restrictions that apply to the use of herbicides. Consult a licensed herbicide applicator before applying herbicides over large areas.

Materials developed by the Maine Natural Areas Program for use by University of Maine Cooperative Extension. This fact sheet was made possible by a gift from New England Grows.

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